I suppose it depends in part on HOW the kids are doing it. Are they big enough to know better and running fast with sticks? That's definitely NOT OK.
Are they 2 years old and just wanting to get close enough to hug them? Well, probably still not OK from the chickens point of view, but I'd...
Kids may find this fun - chickens probably do not. In my case, my girls don't chase the chickens. But I had a nephew visit and chase them around. The rooster got very defensive - and flattened my nephew. He didn't draw blood - just left some big ole foot prints on his chest and knocked him...